1. Technical Field
This invention relates to furnaces and the cooling thereof. More particularly, this invention relates to an accelerated gas cooling system for a furnace or like heating system. Specifically, the invention is a method and apparatus for accelerated cooling of a heating system such as a susceptor heating system.
2. Background Information
It is well known that furnaces or other heating systems are used to heat materials and parts to very high temperatures for a variety of reasons such as heat treating, annealing, curing, baking on coatings, masking, tempering, purification, application of graphite, or hardening. Typically, materials or parts are placed in the furnace that is sealed from the atmosphere or under positive vacuum and thereafter heated to hundreds or thousands of degrees. Once the process is complete, the furnace must cool prior to opening and removing the treated materials and parts. This cooling process is often very time consuming and in many cases may takes hours, days or weeks.
Certain types of newer induction furnaces or susceptor systems provide gas cooling systems in various forms for use with induction systems including vacuum chambers and/or steel walled vessels. In these systems, the heat exchange medium is gas that is either re-circulated across an inner water cooled wall surface or forced outside the chamber through a heat exchanger.
However, many induction heated susceptor systems are designed without vacuum chambers and/or steel walled vessels. These systems are still in use and continue to be supplied as new and operate where they provide desirable processing of parts; however its users desire to reduce the time required for cool down to a temperature where the furnace may be disassembled or otherwise opened so that unloading and handling of the finished materials and parts may occur. As noted above, often this cooling time is hours or days, and in some cases may take a week or longer. An accelerated or more rapid cooling is desired but must be accomplished without opening the system to the atmospheric air as such opening prior to proper and complete cooling to the oxidation temperature or below may cause metallurgical, chemical or oxidation of the product or susceptor.
The alternatives of using a xe2x80x9conce throughxe2x80x9d inert gas flow takes excessively long and results in significant capture costs where done properly to be environmentally safe. In most instances, venting of the inert gas is illegal so this is not an option.
It is thus very desirable to discover a method of accelerated cooling for use with the many induction heated susceptor systems that were designed without vacuum chambers and/or steel walled vessels.
The present invention is a method and apparatus for accelerated cooling of a heating system such as a susceptor heating system.
Specifically, the invention includes a heat chamber, a cooling gas circulator fluidly connected to the heat chamber for providing a first portion of cooling gas thereto, a bypass whereby a second portion of the cooling gas bypasses the heat chamber and is merged back in with the first portion of the cooling gas that was provided to the heat chamber after the first portion has exited the heat chamber, and a heat exchanger for removing heat from the cooling gas after the first portion has exited the heat chamber and prior to re-circulating of the cooling gas into the cooling gas circulator.
The present invention is also a method for accelerated cooling of a furnace, the method including the steps of circulating a first portion of cooling gas to a heat chamber after heating of the heat chamber has been completed, bypassing a second portion of the cooling gas around the heat chamber, merging the first portion of the cooling gas that was provided to the heat chamber with the second portion of cooling gas that bypassed the heat chamber, and removing heat from the cooling gas after merging the first portion that has exited the heat chamber with the second portion that bypassed the heat chamber.